200-ton Tractor if New Douglas Rang(
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Three New Specialized Vehicles Built for Exceptional Conditions Form the Basis of Series with Various Wheelbases and having a Choice of Proprietary Engines
AA FOUR-WHEEL-tractor with power-assisted steering and 160 h.h.p. engine, a special sixwheel-drive oilfields vehicle and a light six-wheeler with bogie drive, have now been added to the range of vehicles built by Douglas equipment, Ltd., Cheltenham. The tractor, known as the " Tugmaster," can he equipped with an
• eight-cylindered petrol engine or six cylindered oil engine. This unit has been designed for use in factories, air. fields, and docks, and it can haul railway trucks of up to 200 tons total load.
Any proprietary make of engine can be fitted to this tractor. The drive is taken through a fluid coupling and fourspeed epicyclic pre-selective gearbox to a Douglas two-speed auxiliary transfer box in which front-wheel drive can be selectively engaged in the direct or indirect ratios. With the 160 b.h.p. petrol engine and main gearbox ratios of 6.385. 4.5, 2.53 and 1.637 to 1 and direct drive, and a ratio of 3.89 to 1 the transfer box, the Tugmasier has speed ' range from . 1.185 m.p.h. 30 rn.p.h when fitted with 12.00-20-i tyres. Twin tyres are uSed at the re and the maximum tractive effort 19,980 lb.'
Special axles built for this model ha bevel-.and-huh reduction, giving an ove all ratio of 7.48 to 1. Worm-and-n steering gear is fitted and assistance provided by Stein Atkingson gear mounted outside the seerli column and taking effect on the pus pull rod.
Measuring 17 ft; in overall length, tl tractor has a 9-ft. wheelbase. Norm control with right-hand steering is pr vided, and the engine iS sited practical
• ahead of the front axle to improve tra tion. Westinghouse air-pressure bra! jug equipment is employed, including 7-cu.-ft. air compressor and a st ndai twin break-away coupling for trail braking equipment.
The Tugmaster weighs about 10 to and is arranged for a crew of foi and has ballast containers on each sic with provision for sand or gravel to t scattered under the wheels to gii adhesion on slippery roads. Two to ing loops are arranged at the fror whilst at the rear-a spring-loaded jai 33 in. above ground level, is availab to take a drawbar or trailer coupling.
Additional equipment, including rear-mounted winch and anchor, is ah offered. A 60-gallon fuel tank mounted across the chassis behind LI cab.
The Douglas heavy-duty six-whee drive cross-country chassis for loads t 15-22 tons has a two-piece chassis fran combining the standard 12-in. den longitudinals to carry the engine and nain components, with a 211-in.-deep pressing bolted and welded to it to provide the requisite strength and to supPort concentrated loads.
This model, is available in Various wheel bases and overall lengths. For oilveil servicing rigs a 20-ft. wheelbase provided in a chassis 38 ft. 4 in. long, vith a 10-ft. 6-in, rear overhang from he centre line of the bogie.
In the current production models an 9.6-litre 125 b.h.p. oil engine, :77lutch and four-speed gearbox arc lited. The transmission is through a Douglas two-speed transfer box, with atios of 3.89 and 1 to 1. Front-wheel lrive is selective in the higher ratio and positively engaged in the indirect gear. A modified Kirkstall bogie, having
werhead worm drive of 825 to I ratio, s fitted at the rear, whilst the front axle las a double-reduction bevel and louble-helical-gear drive of 7.9 to 1. kdjustment between the axle ratios is nade in the transfer box. For oilfield
• equirements the bogie has solid-beam .uspension.
The chassis can be provided with lormal or full forward control, the !urrent series having left-hand-drive teering and a Bonallack cab with :anopy and sun visor. Power-assisted leering gear is available, the equipment 'icing Stein Atkingson or Lockheed tydraulic, Westinghouse air-pressure waking gear is standard. The makers lffer 15.00-20 in. single tyres all round, ir 14.00-20 in. at the front and 11.00'A in, twins for the bogie.
A Douglas conversion of a 5-ton
tandard chassis to four-wheel drive, or or use as a 6x 4 or a 6 x 6, has been )1anned, employing parts common to ill three. Alternatively, the components an be used to build light four-wheeled ind six-wheeled cross-country vehicles. vith a proprietary engine in a Douglas :hassis.
In the conversion models the frame is .tripped and rebuilt, with additional wrapping longitudinals and more cross-members, two of which are placed to support the transfer box close behind the main gearbox. The Douglas transfer box is adaptable to four-wheel or six-wheel drive and has a full-enginetorque power take-off which can be mounted at the top or sides. This leaves the main gearbox power take-off for operating a self-recovery winch.
When the Douglas bogie is fitted, the transmission is taken through twin propeller shafts. One is directly connected to the centre axle and the other linked to the third axle from a second flange at the rear of the transfer box, and passed 'over the centre axle, A short jackshaft, carried by a bracket with opposed taper-roller races, is attached
to the centre axle to link the transferbox prOpelter shaft to the third axle.
The bogie has a single semi-elliptic spring on each side, carried in a centre trunnion. It is not shackled at the axles, the positions of which are controlled through upper and lower torque rods. These serve the dual purpose of controlling driving and braking torque. Steel check straps limit bogie oscillation to 9 in.
As applied to Commer Superpoise. 5-ton chassis, 50 of which are at present being converted to six-wheelers with bogie drive, the frame is wrapped with a pressed-steel member, attached by fitted bolts, and Manes heavy-dilly steering gear and a new push-pull rod and drop arm are provided. Woodhead trunnion-cnded spring's and doubleacting telescopic front shock absorbers are used at the front.
The normal brake-servo unit is rep!aced. by one of larger capacity to accommodate the bogie, which has G rl ing hydraulically operated two-leading-shoe operation. The bogie drum diameter is 16 in. and • the shoes are 41 in. wide. Tyres ranging from 8.25 in. to 11.00-20 in. can be supplied. The bogie-axle centres are 4 ft. and the mean wheelbase is 13 ft. 9 in., or it can be arranged to suit special requirements.
The Douglas front or bogie axles have bevel drive, the standard • ratio being 7.14 to 'I. The bogie track is 6 ft. 11 in. and the front track 6 ft. 41 in. Standard transfer-box ratios of direct drive and 2204 to 1 are specified and the box has selective front-wheel engagement, where front-wheel drive is fitted, in both ratios.
The tractive effort depends on the type of chassis employed, but the normal bogie conversion is rated for 8-10-ton loads. About 6-7 tons of payload can be carried across country.